Method of insulating electrical conductors.



PATENT oFFIoE.

UNITED STATES WILLIAM H. BRISTOL, OF NEW YORK, N. Y. METHOD oFINSULATING ELECTRICAL CQNDUOTORS- No. 798,260. I

Specification of Letters Patent.

Patented Aug. 29, 1905,

Application filed December 3, 1904- Serial No. 235,346-

To all whom it may concern:

Be it known that 1, WILLIAM H. BRISTOL, a citizen of the United Statesof America, residing at New York city, in the county of New York. andState of New York, have in- Vented certain new and useful Improvementsin Methods of Insulating Electrical Conductors, of which the followingis a specification.

My invention relates to a method of insulating electrical conductors,and in particular to conductors in which the electric current is used togenerate heat or in which heat is used to generate an electric current,such as resistance-coils, electric heaters, thermo-electric generators,and pyrometers.

My method consists, essentially, in forming an insulating material inthe condition of a paste or paint and which on drying forms a hard,fireproof, and electrically-non-conductive material, then applying thispasteor paint to the conductors to be insulated so as to embed themtherein, and finally heating "the whole to dry and harden it.

The insulating material consists of a mixture of a finely-powderedfire-resisting material which is substantially non-conductiveelectrically-such as carborundum, corundum, .clay, &c., or a .mixture ofone or more of these-with a solution of silicate of soda, which actsas,a binder for the loose material.

is ground inany convenient manner to a fineness of from 1 F. to 3 F. Thedry silicate of soda is also powdered, but not necessarily to such adegree of fineness as the fire-resisting material, and the constituentsare then intimately mixed in the proportion of from one to twenty parts,by weight, of fire-resisting material to one part, by weight, of thesilicate of soda. soda depends upon the use lating material is to beput. temperatures the The proportion of the silicate of electricity. Bylowering the proportion of slicate of soda, however, the strength of thematerial is impaired and it tends to crumble. When ready to be applied,a sufiicient quantity of the mixture is taken and thoroughly stirredwith enough water to give the desired consistency. It is, however,usually more convenient to use the commercial water solution of thesilicate, which is of about 1.4 specific gravity. The powderedfire-resisting material in this case is mixed with the solu- Thecarborundum or other fire-resistlng material i to which the insu- Forvery high proportion of silicate of soda should be comparatively low, asthe mass otherwise becomes plastic and a conductor of tion to thedesired consistency. The solution may of course be diluted with water tolower the proportion of silicate. In applying this material to theconstruction of an electric heater or resistance-coil a thin sheet ofasbestos or mica or a slab made of the said insulating material is takenand about this or an insulated form is wound a layer of theresistance-wire. This layer is then painted with a thin coat of theinsulating material, which is allowed to dry and harden. Another layerof ,wire is then wound around the former and another coat of insulatingvmaterial applied, &c.

After being applied the material is dried by heating, either by acurrent of electricity of gradually-iricreasingstrength passing throughthe conductors or by applying heat externally to the entire mass. Ondrying it forms a hard compact mass electrically non-conductive andcapable of resisting high temperatures, especially such temperatures asare encountered in electric heating apparatus and the like. In someinstances it is advantageous to give the surface a glaze or to coat itwith a varnish or the like in order to render it completely imperviousto moisture.

By mixing the solution of silicate of soda with finely-powderedcarborundum or corundum or clay, &c., or a mixture of these a paste orpaint is obtained which can very readily be applied and which permeatesthe spaces between the conductors, completely insulating them and alsoforming a protective covering for the conductors themselves. The massdoes not crack nor deteriorate under severe tests. Asbestos fiber,thread or sheet, can frequently be used to advantage in connection withthis insulating material.

In winding a resistance-coil, electric heater, or the like a thin sheetof asbestos may be placed over each layer of wire and insulatingmaterial before applying the next layer of wire and insulating material.This sheet of asbestos serves to prevent any possible short circuitingduring the winding due to the insulating material not having completelyhardened and'makes it unnecessary to wait for the 1 insulating materialto become perfectly hard before Winding on the succeeding layers ofresistance-wire. The insulating material soaks through the asbestos andmakes a solid mass i of the whole, firmly embedding the conduc l torstherein and insulating them. The insulating material is also very welladapted for I protecting the elements of a thcrmo-electric couple, suchas used in electric pyromcters or lated.

in thcrmo-electric generators. The elements of such a couple may be veryeffectively protected and insulated by simply dipping such a couple orseries of couples into a bath of the insulating material and thenwithdrawing it and 'allowing it to hardenand then finally subjecting itto heat. Of course the couple may firstbe wound with an asbestos threador strip and then dipped, or the insulating material may simply beapplied as a paste or paint to the parts to be protected and insu- WhatI claim as my invention, and desire to secure by Letters Patent, is

1. The herein-described method of electrically insulating conductors,which consists in forming an intimate mixture of a powdered fireresisting material, electrically non-com ductive, with a solution ofsilicate of soda, wrapping asbestos about said conductors, applying saidmixture in the form of a paste or paint so as to embed said conductorstherein, and finally heating todry and harden said material.

2. The herein-described method of electric-- ally insulating conductors,which consists in forming an intimate mixture of powdered carborundumwith a solution of silicate of soda to the desird consistency; thenapplying said mixture to said conductors so as to-em bed them withinsaid mixture, and finally heating to dry and harden the whole. 7

3. The herein-described method of electrically insulating conductors,which consists in forming an intimate mixture of powdered carborundumwith a solution of silicate of soda, wrapping asbestos about saidconductors, applying said mixturein the form of a paste or paint so asto embed said conductors therein, and finally heating to dry and hardensaid materia 4. The herein-described method of electrically insulatingconductors, which consists in forming an intimate mixture of powderedcarborundum and a solution of silicate of soda,

applying this material in the form of a paste or paint so as to embedsaid conductors therein; and finally heating the whole and glazing thesurface thereof.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this lst day of December, 1904.

WILLIAM H. BRISTOL;

. Witnesses;

FREDK. F. SCHUETZ, ROENA H. YUDIZKY.

